The removal of elemental mercury (Hg-0) by KI and KBr modified clays (KI-clays and KBr-clays) was studied under simulated flue gas conditions. The physicochemical properties of these catalysts were investigated by a variety of characterization methods. The effects of KI and KBr loading, adsorption temperatures and the flue gas components (such as O-2, SO2 and H2O (g)) on Hg-0 removal efficiency were investigated. A pseudo-second-order model simulation was also introduced to reveal the mechanisms of Hg-0 removal. The results showed that the Hg-0 removal efficiency for the clays was significantly enhanced by KI or KBr modification, and the KI-clays performed much better than the KBr-clays in terms of Hg-0 removal under the same conditions. An increase in KI or KBr loading and adsorption temperatures improved the Hg-0 removal efficiency, which indicated that chemisorption occurred. The presence of 02 and SO2 promoted Hg-0 removal, whereas the presence of H2O inhibited Hg-0 removal by these modified clays. The formation of Hg-0 from the reaction (2KI + 1/2O(2) <-> I-2 + K2O) was considered to be an important step in the chemisorption of Hg-0 on the surfaces of the KI-clays. The lower extent of Hg-0 removal exhibited by the KBr-clays than by the KI-clays was due to the difficulty of Br-2 formation on the surfaces. The pseudo-second-order model was demonstrated to simulate with the removal of Hg-0 by KI-clays and KBr-clays well. The KI-clays displayed much a higher of the initial adsorption rate (H) and Hg-0 removal capacity (q(e)) than the KBr-clays under the same conditions, which demonstrated that KI-clays are more active than KBr-clays with respect to Hg-0 removal. (C) 2013 Elsevier B.V. All rights reserved.